The QMG scoring system consists of 13 items: ocular (2 items), facial (1 item), bulbar (2 items), gross motor (6 items), axial (1 item), and respiratory (1 item). Each item is graded from 0 to 3, (0 = none, 1 = mild, 2 = moderate, and 3 = severe). The range of total QMG score is 0 to 39, with higher scores indicating more severe disease.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The MG-ADL is an 8-point questionnaire that focuses on relevant symptoms and functional performance of activities of daily living in participants with myasthenia gravis (MG). The 8 items of the MG-ADL are derived from symptom-based components of the original 13-item QMG to assess disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. In this functional status instrument, each response is graded from 0 (normal) to 3 (most severe). The range of total MG-ADL score is 0 to 24, with higher scores indicating more severe disease.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The MG-ADL is an 8-point questionnaire that focuses on relevant symptoms and functional performance of activities of daily living in participants with MG. The 8 items of the MG-ADL are derived from symptom-based components of the original 13-item QMG to assess disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. In this functional status instrument, each response is graded from 0 (normal) to 3 (most severe). The range of total MG-ADL score is 0 to 24, with higher scores indicating more severe disease.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The MG-ADL is an 8-point questionnaire that focuses on relevant symptoms and functional performance of activities of daily living in participants with MG. The 8 items of the MG-ADL are derived from symptom-based components of the original 13-item QMG to assess disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. In this functional status instrument, each response is graded from 0 (normal) to 3 (most severe). The range of total MG-ADL score is 0 to 24, with higher scores indicating more severe disease.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The QMG scoring system consists of 13 items: ocular (2 items), facial (1 item), bulbar (2 items), gross motor (6 items), axial (1 item), and respiratory (1 item). Each item is graded from 0 to 3, (0 = none, 1 = mild, 2 = moderate, and 3 = severe). The range of total QMG score is 0 to 39, with higher scores indicating more severe disease.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The QMG scoring system consists of 13 items: ocular (2 items), facial (1 item), bulbar (2 items), gross motor (6 items), axial (1 item), and respiratory (1 item). Each item is graded from 0 to 3, (0 = none, 1 = mild, 2 = moderate, and 3 = severe). The range of total QMG score is 0 to 39, with higher scores indicating more severe disease.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The MGC is a validated assessment tool for measuring clinical status of participants with MG. The MGC assesses 10 important functional areas most frequently affected by MG: ocular (2 items), facial (1 item), bulbar (3 items), respiratory (1 item), axial (1 item), and gross motor (2 items). The scales are weighted for clinical significance that incorporates patient-reported outcomes. The MGC total score ranges from 0 to 50, with lower scores indicating less functional impairment and higher scores indicating greater functional impairment.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The EQ-5D-Y is a reliable and validated survey of health status in 5 areas: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, each of which is completed by the participant for participants ≥12 years of age (at time of assessment) and completed by the participant's caregiver or with caregiver assistance for participant <12 years of age. Each area has 3 levels: Level 1 (no problems), Level 2 (some problems), and Level 3 (extreme problems). The EQ visual analogue scale (VAS) records the participant's self-rated health on a vertical, 20-centimeter VAS where the endpoints are labelled 'Best imaginable health state, marked as 100' and 'Worst imaginable health state, marked as 0'.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The Neuro-QoL Pediatric Fatigue questionnaire is a reliable and validated brief 11-item survey of fatigue, completed by the participant for participants ≥12 years of age (at time of assessment) and completed by the participant's caregiver or with caregiver assistance for participants <12 years of age. Each item was scored on a scale of 1 to 5 (1=Not at all, 2=A little bit, 3=Somewhat, 4=Quite a bit, 5=Very much). Total score is the sum of each item's score and it ranges from 11 to 55. Higher scores indicate greater fatigue and greater impact of MG on activities.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Overall Number of Participants Analyzed' signifies those participants who were evaluable for this outcome measure.

The MG clinical state (improved, unchanged, and worse) was assessed using the MGFAPIS.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Number Analyzed' and 'Overall Number of Participants Analyzed' signify those participants who were evaluable for this outcome measure.

Rescue therapy (for example, high dose corticosteroid, plasma exchange, or intravenous immunoglobulin) was to be allowed when a participant experienced clinical deterioration. Clinical deterioration was defined as follows: Participants who experienced an MG crisis, which was defined as weakness due to MG that was severe enough to necessitate intubation or to delay extubation following surgery; or, Significant symptomatic worsening that required rescue medication in the opinion of the Investigator; or, Participants for whom the Investigator believed that the participants' health was in jeopardy if rescue therapy was not given.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab.

Pharmacokinetic Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab and who had PK data assessments during the study. Here, 'Number Analyzed' signifies those participants who were evaluable for this outcome measure.

Pharmacodynamic Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab and who had PD data assessments during the study. Here, 'Number Analyzed' signifies those participants who were evaluable for this outcome measure.

Pharmacodynamic Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab and who had PD data assessments during the study. Here, 'Number Analyzed' signifies those participants who were evaluable for this outcome measure.

The QMG scoring system consists of 13 items: ocular (2 items), facial (1 item), bulbar (2 items), gross motor (6 items), axial (1 item), and respiratory (1 item). Each item is graded from 0 to 3, (0 = none, 1 = mild, 2 = moderate, and 3 = severe). The range of total QMG score is 0 to 39, with higher scores indicating more severe disease.

Modified Full Analysis Set: all participants 12 to <18 years of age who received at least 1 dose of eculizumab. Here, 'Number Analyzed' and 'Overall Number of Participants Analyzed' signify those participants who were evaluable for this outcome measure.